DESCRIPTION: The proposed research involves investigating the molecular mechanisms which control the selective degradation of peroxisomes in Pichia pastoris. It is proposed to isolate mutants that are defective in the degradation of methanol degrading peroxisomes and to characterize these biochemically and cytologically. The peroxisome degrading genes will be isolated by functional complementation, sequenced and the amino acid sequence deduced. Mutant and wild type sequences will be compared to provide insight concerning function. The second aim of the proposed research is to isolate peroxisome biogenesis defective mutants via the development of new approaches for positive selection. The physiological characteristics of these mutants will be studied.